“We have many candidates and hope to have multiple winners,” Fauci told a Senate committee on Tuesday, as he outlined the relatively rapid pace of development of a vaccine and treatment for the virus.

He also warned that there were potential downsides.

“I must warn that there is also the possibility of negative consequences, where certain vaccines may enhance the negative effect of the infection,” he said. “The big unknown is efficacy. Will there be presence or absence, and how durable will it be?”

He also said that it was “a bit of a bridge too far” to expect that a vaccine or treatments available to assist students when they go back to school for the fall school term.

Testifying via remote video to the Senate Health, Education, Labor and Pensions Committee, Fauci also said that the number of coronavirus deaths is likely higher than has been reported. According to Johns Hopkins University, more than 80,000 people in the U.S. have died after contracting the virus.

He also warned of states and localities jumping the gun on reopening. “My concern is that we will start to see little spikes that might turn into outbreaks,” he said.

At one point in the hearing, Sen. Rand Paul (R-KY), who contracted the coronavirus and has recovered, told Fauci that he didn’t think “you’re the end all. I don’t think you’re the one person that gets to make a decision.”

“I have never made myself out to be the end all, the only voice in this,” Fauci responded. “I am a scientist, a physician, a public health official. I give advice according to the best scientific evidence.”

Later at the hearing, Sen. Mitt Romney (R-UT) was critical of the Trump administration’s claims on testing capacity.

After Brett Giroir, assistant secretary for health at the Department of Health and Human Services, said on Monday that the U.S. has conducted more tests per capita than South Korea, Romney said to him during the hearing, “You ignored the fact that they accomplished theirs at the beginning of the outbreak, while we treaded water during February and March. And as a result by March 6th, the U.S. had completed just 2,000 tests, whereas South Korea had conducted more than 140,000 tests. So partially as a result of that, they have 256 deaths and we have almost 80,000 deaths. I find our testing record nothing to celebrate whatsoever.”

PREVIOUSLY, 6:17 AM PT: Anthony Fauci, a member of President Donald Trump’s coronavirus task force, plans to warn of the risks of reopening the country too soon in an appearance on Tuesday before a Senate Committee.

The hearing of the Senate Health, Education, Labor and Pensions Committee will be closely watched. In addition to coverage on cable news networks, NBC News plans to carry it, with Lester Holt anchoring a special report. ABC News will carry it on their streaming channel ABC News Live, and break in if necessary for special reports.

Fauci, the director of the National Institute of Allergy and Infectious Diseases, wrote in an email to The New York Times on Monday that he wants to convey “the danger of trying to open the country prematurely. If we skip over the checkpoints in the guidelines to ‘Open America Again,’ then we risk the danger of multiple outbreaks throughout the country. This will not only result in needless suffering and death, but would actually set us back on our quest to return to normal.”

Trump has been pressuring some states to reopen their economies, even while the White House has created a set of guidelines on reopening. In a memo, Attorney General William Barr has directed top federal prosecutors to “be vigilant to ensure its protections are preserved, at the same time that the public is protected.”

Fauci will be testifying remotely, as the Senate grapples with how to conduct its business in the midst of the coronavirus epidemic. Fauci has been in “modified quarantine” after coming into some contact with a White House staffer who later tested positive for the virus.

Also testifying remotely before the committee will be Robert Redfield, the director of the Centers for Disease Control; Brett Giroir, assistant secretary for health at the Department of Health and Human Services; and Stephen Hahn, commissioner of the Food and Drug Administration. The chairman of the committee, Sen. Lamar Alexander (R-TN), also will appear via video, after he went into self quarantine when one of his staffers tested positive.